In numerous applications such as liquid level sensing or hydraulics, it may be desirable to measure linear displacement of an object. One conventional device for measuring linear displacement is a magnetostrictive sensor. Magnetostrictive sensors generally employ a magnetostrictive wire which runs in a straight line or curved path through a measurement area. In conjunction with this wire, the object to be measured may be provided with a magnet, which induces a torsional strain in the magnetostrictive wire when the wire is subject to an electrical signal. The position of the magnet represents the position of the monitored object, and is determined as a function of the time required for the torsional motion of the magnetostrictive wire to propagate from the area of influence of the magnet to a sensing apparatus located at one end of the wire. Alternatively, a torsional excitation signal may be imparted to the wire. When the torsional excitation signal passes the magnet, the magnet induces an electrical signal in the wire, which may be detected to determine the position of the magnet. Exemplary magnetostrictive sensors for use in linear displacement detection applications is disclosed in U.S. Pat. No. 5,017,867 to Dumais et al., the contents of which are incorporated by reference herein.
Magnetostrictive sensors may suffer from a number of problems in linear displacement sensing applications. As an example, when the monitored object is positioned too close to the end of the wire at which the sensing apparatus is positioned, the resulting torsional motion may be difficult to accurately detect, resulting in inaccurate sensing of linear displacement. Thus, improvements in such sensors are desired.